My trusty +1 weapon.
Truth be told, I don't really have a favorite item. I got burned by the wackiest of them back in high school that I now favor the simple stuff. That is a good story I'll have to tell you one day.
Axe of the Dwarvish Lords - It was always the desire of my character to obtain this grand artifact, and he finally did at 15th level after a grand and glorious quest (circa 1983)